U.S. patent application number 10/674116 was filed with the patent office on 2005-11-24 for techniques for labeling of plastic, glass or metal containers or surfaces with polymeric labels.
Invention is credited to Dronzek, Peter J. JR..
Application Number | 20050257882 10/674116 |
Document ID | / |
Family ID | 35374059 |
Filed Date | 2005-11-24 |
United States Patent
Application |
20050257882 |
Kind Code |
A1 |
Dronzek, Peter J. JR. |
November 24, 2005 |
Techniques for labeling of plastic, glass or metal containers or
surfaces with polymeric labels
Abstract
The invention provides a method for labeling a glass, plastic or
metal container or surface with a polymeric label by means of a
water based adhesive composition by the following steps: (a)
selecting a polymeric label having a density of less than 0.9; (b)
applying a water based adhesive to said polymeric label to form a
fastenable polymeric label; (c) fastening said fastenable polymeric
label to a glass, plastic or metal container or surface; and (d)
allowing said polymeric label to dry on said glass, plastic or
metal surface or container.
Inventors: |
Dronzek, Peter J. JR.;
(Thornwood, NY) |
Correspondence
Address: |
HEDMAN & COSTIGAN P.C.
1185 AVENUE OF THE AMERICAS
NEW YORK
NY
10036
US
|
Family ID: |
35374059 |
Appl. No.: |
10/674116 |
Filed: |
September 29, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10674116 |
Sep 29, 2003 |
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10292231 |
Nov 12, 2002 |
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Current U.S.
Class: |
156/272.2 ;
156/275.5; 156/275.7; 428/195.1 |
Current CPC
Class: |
B65C 3/06 20130101; Y10T
428/24802 20150115; B65C 9/22 20130101 |
Class at
Publication: |
156/272.2 ;
156/275.5; 156/275.7; 428/195.1 |
International
Class: |
B32B 031/00 |
Claims
1. A method of labeling a glass, plastic or metal container or
surface by means of a water based adhesive composition, said method
comprising: (a) selecting a microvoided polymeric film label; (b)
applying a water based adhesive to said microvoided polymeric label
to form a fastenable microvoided polymeric label; (c) fastening
said fastenable microvoided polymeric label to a glass, plastic or
metal container or surface; and (d) allowing said polymeric label
to dry on said glass, plastic or metal surface or container.
2. A method for labeling a glass, plastic or metal container as
defined in claim 1 wherein a hydrophilic layer is applied to said
microvoided polymeric film before said water based adhesive is
applied.
3. A method for labeling a glass, plastic or metal container as
defined in claim 2 wherein water is applied to said hydrophilic
layer to form a fastenable microvoided polymeric label.
4. A method for labeling a glass, plastic or metal container as
defined in claim 2 wherein a waterbased adhesive containing a
catalyst is applied to said hydrophilic layer to form a fastenable
microvoided polymeric label.
5. A method for labeling a glass, plastic or metal container as
defined in claim 2 wherein the reactive catalyst is crosslinkable
with either the hydrophilic layer the adhesive layer or both
layers.
6. A method for labeling a glass, plastic or metal container as
defined in claim 2 wherein the hydrophilic layer is a coated,
coextruded or extruded layer.
7. A method for labeling glass, plastic or metal container as
defined in claim 6 where hydrophilic layer is a coated layer.
8. A method for labeling a glass, plastic or metal container as
defined in claim 2 wherein the adhesive is applied with 100%
coverage or a pattern to the hydrophilic layer.
9. A method for labeling a glass, plastic or metal container as
defined in claim 2 wherein less adhesive is applied than is
normally applied to a paper label.
10. A method for labeling a glass, plastic or metal container as
defined in claim 2 wherein the microvoided polymeric label is a
mono-layer or coextruded film selected from white or colored
cavitated polypropylene, polyethylene, polyester, polystyrene or
polycarbonate.
11. A method for labeling a glass, plastic or metal container as
defined in claim 2 wherein the microvoided polymeric label includes
a reverse printed clear polymeric film which is laminated to the
microvoided polymeric label surface.
12. A method for labeling a glass, plastic or metal container as
defined in claim 2 wherein an adhesion promoting tie layer or
primer is used to promote adhesion of the hydrophilic layer to the
microvoided polymer label.
14. A method for labeling a glass, plastic or metal container as
defined in claim 2 wherein an adhesion promoting layer is used on
the print surface on the microvoided polymer label to promote
indicia adhesion.
15. A method for labeling a glass, plastic or metal container as
defined in claim 2 wherein a protective coating over the surface of
the printed indicia is formulated with slip aids and/or anti-static
agents to control the coefficient of friction and static properties
between the hydrophilic layer and protective coating for optimum
high speed application.
16. A method for labeling a glass, plastic or metal container as
defined in claim 2 wherein a protective coating over the surface of
the printed indicia is formulated with anti-block and/or anti-stick
aids to control the blocking tendency of the moisture activated
hydrophilic layer for optimum high speed application.
17. A method for labeling a glass, plastic or metal container as
defined in claim 2 wherein a protective coating over the surface of
the exposed polymer layer is formulated with slip aids and/or
anti-static agents known to those in the art to control the
coefficient of friction and static properties between the
hydrophilic layer and protective coating for optimum high speed
application.
18. A method for labeling a glass, plastic or metal container as
defined in claim 2 wherein a protective coating over the surface of
the exposed polymer layer is formulated with anti-block and/or
anti-stick aids to control the blocking tendency of the moisture
activated hydrophilic layer for optimum high speed application.
19. A method for labeling a glass, plastic or metal container as
defined in claim 2 wherein the hydrophilic layer is formulated with
humectants for curl control and/or anti-block aids to control the
layflat and blocking properties of the label for optimum high speed
application.
20. A method for labeling a glass, plastic or metal container as
defined in claim 2 wherein the aqueous label adhesive is based on
starch, casein, synthetic polymer or blends of starch, casein or
synthetic polymers.
21. A method for labeling a glass, plastic or metal container as
defined in claim 2 wherein the hydrophilic layer activated by water
into an adhesive layer is a derivative of polyacrylic acid or
polyacrylic acid copolymer.
22. A method for labeling a glass, plastic or metal container as
defined in claim 21 wherein the hydrophilic layer activated by
water into an adhesive layer is a carboxylated sodium
polyacrylate.
23. A method of labeling a glass, plastic or metal container or
surface by means of a water based adhesive composition, said method
comprising: (a) selecting a microvoided polypropylene label; (b)
applying a water based adhesive to said microvoided polypropylene
label to form a fastenable label; (c) fastening said fastenable
label to a glass or plastic container or surface; and (d) curing
said microvoided polypropylene label on said glass or plastic
container or surface.
24. A plastic metal or glass container having a polymer label
comprising a microvoided polymer, a dried water based adhesive
which affixes said microvoided polymer label to said container,
said microvoided polymer label containing a portion of said dried
water based adhesive within said microvoided polymer.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a method of labeling containers
with polymeric materials particularly adapted for use as labels in
the post mold labeling of plastic, glass or metal containers or
surfaces. More particularly, the present invention relates to the
use of particular low density polymeric film substrates adapted for
printing that may also have a hydrophilic surface layer for use as
labels in post mold labeling applications using conventional wet
applied water based labeling equipment and solutions typically used
for the application of paper labels. In another aspect the
invention relates to such labels which possess the beneficial
properties of the known plastic label substrates, but which are
able to be applied on conventional post mold paper labeling
equipment using wet applied water based solutions comprising water,
water blended with a selected catalyst, adhesives or adhesives
blended with a selected catalyst and are adapted to facilitate the
recycling process when the labels are applied to certain types of
containers.
BACKGROUND OF THE INVENTION
[0002] Plastic and glass containers or bottles are prevalent in a
wide variety of shapes and sizes for holding many different types
of materials such as detergents, chemicals, motor oil, beer, etc.
These containers are glass or plastic (mono or multi layers) of
polyethylene, polypropylene, polyester or vinyl along with other
specialty blends for specific barrier and product resistance
performance. Generally such containers are provided with a label
which designates the trade name of the product and may contain
other information as well. The early art which still is prevalent
today employed the use of labels manufactured from paper substrates
that were applied with a water based adhesive. Subsequently, dry
pressure sensitive self adhesives and in mold labels manufactured
from paper have been and continue to be used. The shortcomings of
paper labels with regard to tearing, wrinkling, creasing and the
like due to age and moisture, or due to a lack of deformability
when applied to a deformable plastic substrate have been well
documented in the labeling industry. Because of this and the need
to produce recyclable plastic containers, over the years a great
deal of effort has been expended to develop container decoration
techniques and durable polymeric film substrates or face stocks
which would overcome these shortcomings. Film facestocks for
container decoration which have resulted from these efforts can be
applied to glass and plastic containers as self adhesive pressure
sensitive labels as described in the prior art. The use of self
adhesive paper and film "pressure sensitive adhesive" (PSA) labels
that have been preprinted and supported on a release liner is not a
cost effective option because of the added cost of the release
liner used to support and render processable the self adhesive face
stock. The cost of this type of structure combined with the added
cost of disposal of the liner does not make pressure sensitive
labeling a desirable option from an economic or environmental
standpoint. In addition, new capital intensive labeling equipment
is required to transition from wet applied Post Mold Labels (PML)
to self adhesive PSA labels plus the effect of a new process on an
existing packaging line in terms of learning cure and experience.
Cut PML labeling equipment typically will run to six times the
speed of a PSA labeling system.
[0003] Another film face stock labeling technique that has evolved
is the use of heat activated in-mold labels as described in the
prior art where a preprinted plastic label with a heat activated
adhesive on the back of the label is placed in the mold before the
molten plastic resin is injected or blown into the mold cavity at
elevated temperature and pressure which activates the adhesive and
fuses the label substrate to the container in-mold. The use of film
based in-mold label substrates presents a more cost effective
alternative then self adhesive pressure sensitive labels in terms
of substrate cost but as this technology has progressed, it has
been found that productivity is impacted by the label feeding step
into the mold which is performed in a complex, continuous and rapid
manner which can result in large amounts of scrap material. Also,
the initial capital investment required to tool up for a container
specific in-mold label process for new molds and the complex
electromechanical maintenance intensive feeding devices is
significant. Another detriment for this process is the potential
inventory carrying costs for varieties of labeled containers that
come into play with predecorated containers such as in-mold for
those who would choose to apply the label immediately pre or post
filled.
[0004] Post mold decoration of glass and plastic containers in the
current art can also be accomplished by direct screen printing on
the container. Direct screen printing on the container is not a
cost effective process and also presents the aforementioned
inventory problems along with added cost for freight to and from a
screen printer. The graphical possibilities for label copy are
limited in terms of cost and quality with this technique. Commodity
products can not support the cost of this labeling technique.
[0005] Another post mold technique that has been popular is the
"Thermage" process. This process transfers a reverse printed image
from a transfer release paper under temperature and pressure to
produce decorated containers. The "Thermage" technique of
transferring a reverse printed image is costly because of transfer
release paper costs and presents the same disposal problems and
costs with the transfer sheet as occurs with the aforementioned
release liner used in conjunction with self adhesive labels.
[0006] Other techniques for labeling various plastic and glass
containers with preprinted paper or film label substrates include
the use of hot melt adhesives which are applied to the label
substrate or container in a molten state with container and
substrate subsequently married while the hot melt is molten. When
the hot melt adhesive cools, it sets up and bonds the label
substrate to the container.
[0007] This technology requires the use of sophisticated melting
and application equipment that must be operated, cleaned and
maintained at elevated temperatures. This technology works well
with complete 360 degree wrap around labels but has not evolved to
the point to allow consistent labeling of a die cut or square cut
"patch label" with less than 360 degree wrap. Affixing a patch
label to an area on a container with 100% or patterned adhesive
application using hot melt adhesives has not been commercially
perfected. Complete wrap around hot melt applied labels where one
end of the label is affixed to the container while the other end is
wrapped around the container greater than 360 degrees to form a
glue lap where the trailing edge is affixed with hot melt to the
leading edge of the label substrate is proven hot melt label
application technology that works well for film and paper label
substrates. This labeling technique does not fit for applying patch
labels on individually labeled panels of containers such a
rectangular oil, contoured detergent or beer containers where a
neck and front label only are applied. Another drawback is the
added cost for label substrate when this technique is used since
more label substrate is required because of the 100% wrap
around.
[0008] Lastly, and still one of the most prevalent labeling
techniques is the application of paper based cut patch labels to
glass and plastic containers using natural and synthetic laminating
adhesives such as BL300 produced by Henkel Adhesives or OC353-20
produced by O.C. Adhesives Corp. which are known to the art. This
is a safe (water based) proven technology that has grown and been
employed for many years and consequently there are many existing
machines that have been installed for this type of labeling
technique such as from Krones, Neutraubling, Germany that run
precut patch labels or Koyo, Japan which runs roll stock that is
cut into a rectangular or square patch label on the labeling
machine to the label size. The cut label techniques and associated
adhesives work well with paper based substrates applied to glass or
plastic containers because the wet adhesive wicks (absorbs) into
the paper substrate from the applicator roll, pad or pallet which
breathes and allows the moisture from the water carrier to be
absorbed by and dry thru the paper base.
[0009] This technique obviously will not work with non-porous
polymeric label substrates as the adhesive cannot dry thru (wick
into) the polymeric substrate. The adhesive and polymeric label
substrate must be chosen to have initial tack and adhesive transfer
to the label. Typically, wet applied cut label machines work where
glued pallets remove the label out of the label holding magazine
while simultaneously gluing the back side of the label. This is
accomplished by applying a thin glue film to the pallet which is
then pressed in intimate contact against the first label in the
stack. After its removal, the label sticks on the entire glued area
of the pallet until transferred to a "gripper" cylinder and removed
from the pallet. The gripper cylinder then transfers the label to
the container to be labeled. The various machine designs and
techniques are well known within the labeling industry and to those
skilled in the art. The "Krones Manual Of Labeling Technology" by
Hermann Kronseder dated December 1978, is hereby incorporated by
reference.
[0010] Attempts have been made to use polymeric substrates with
high moisture vapor transmission rates (MVTR) such as films with
micro perforations for drying of the water trapped between the
label and the container and high solids tacky or pressure sensitive
adhesive for good wet tack on conventional wet water based labeling
equipment with little success. The high solids tacky adhesive
required to stick to the polymeric substrate causes machining
problems by gumming up the adhesive application system and creates
cleanup issues. The high MVTR substrates also did not have good wet
tack with existing commercially available adhesives that would
machine without problems and did not dry rapidly enough making the
labels prone to "swimming" or moving from the desired application
area during down stream processing. The micro perforated materials
allow adhesive to ooze thru the label contaminating the label
surface ruining the graphics and making the label sticky. In
addition, many of the current paper adhesives do not wet out and
apply uniformly to non hydrophilic surfaces with the crude adhesive
metering and application systems currently in use on existing paper
labeling machinery. Without uniform application, wet out and wet
tack, it will be impossible to successfully apply a polymeric label
because of adhesive and application imperfections.
[0011] When plastic or glass containers are recycled, the first
step involves cleaning, then label removal and separation of the
labels from the used containers. When polymer labels are removed,
they are sometimes difficult to separate from the
liquid/label/container mixture that is formed during the recycling
process if the density of the polymer label is high enough that it
will not readily separate and float on the surface of the liquid
that is used for label removal. The applicant has discovered that
if the polymer stock for the label is a material having fine micro
voids and a density that is substantially lower than the label
removal fluid, not only will the labels be easily separated from
the container/label/liquid mixture because they float on the
surface of the label removal liquid which simplifies the recovery
of the glass or plastic container for recycling, but the polymeric
labels will also function well in wet glue PML labeling.
[0012] Accordingly, it is an object of the invention to provide a
polymeric label particularly adapted for use in post mold wet
applied labeling of polymeric and glass containers that would
readily feed from the label magazine or gripper, adhere with
sufficient tack without moving through post labeling handling and
processing including but not limited to conveying, filling, case
packing and palletizing and is adapted to recycling.
[0013] It is also an object of the invention to provide a polymeric
label particularly adapted for use in post mold wet applied
labeling of polymeric and glass containers that would have
sufficient wet tack and affinity for water, a water based solution
or adhesive used to allow for transfer of the wet water based
adhesive to the polymeric label substrate from the applicator
roll(s), pad(s) or pallet(s) of the labeling machine and is adapted
to recycling.
[0014] It is also an object of the invention to provide a polymeric
label for use in post mold wet applied labeling of polymeric and
glass containers that would have a coefficient of expansion or
contraction under the conditions which the container sees which is
the same or compatible with that of the polymeric resin, glass or
metal from which the container is made so that expansion and
contraction of the container will not wrinkle or otherwise affect
the integrity of the label and is adapted to recycling.
[0015] It is also an object of the invention to provide a polymeric
label for use in wet applied post mold labeling which would combine
suitable properties of modulus of elasticity and flexibility and
would not be degraded by handling and flexing of the subsequent
container and is adapted to recycling.
SUMMARY OF THE INVENTION
[0016] In considering the performance or economic shortcomings of
prior art materials, I have discovered a process by which a
polymeric label may be applied to a glass, plastic or metal
container or surface by means of a water based adhesive
composition, said method comprising:
[0017] (a) selecting a polymeric label having a density of less
than 0.9;
[0018] (b) applying a water based adhesive to said polymeric label
to form a fastenable polymeric label;
[0019] (c) fastening said fastenable polymeric label to a glass,
plastic or metal container or surface; and
[0020] (d) allowing said polymeric label to dry on said glass,
plastic or metal surface or container.
[0021] The invention also provides a plastic metal or glass
container having a polymer label comprising a low density polymer,
a dried water based adhesive which affixes said polymer label to
said container, wherein said polymer label contains a portion of
said dried water based adhesive within said polymer.
[0022] The use of the low density micro-voided polymer film can
allow portions of the water based adhesive to migrate into the film
during the drying cycle to provide an enhanced bond between the
polymeric label and the container surface and to also impart
stiffness to the dried label on the container surface.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The preferred low density polymeric labels are made of
polypropylene which is commercially available. The preferred
density is 0.55 to 0.85, an especially preferred density is 0.6 to
0.75, as distinguished from the conventional polypropylene label
stock which has a density above 0.9. These materials are sometimes
referred to as cavitated, micro voided or foamed polypropylene.
Other polymers which may be used include polyethylene, polyester,
polystyrene, polycarbonate or compatibilized polymer blends.
[0024] It is preferred to utilize a hydrophilic material in
conjunction with the low density polymeric label to allow for more
rapid escape of water from the water based adhesive that is placed
on the back of the low density polymeric label.
[0025] Hydrophilic materials are selected so that their thickness
and modulus of elasticity when applied to a polymer film will
result in a polymeric film facestock that will have hydrophilicity,
absorbtivity, wet tack and drying properties that will permit the
polymer film to be applied to polymeric or glass containers via
water based wet labeling techniques on standard paper labeling
equipment. The apparatus which is used to apply paper labels is
well known to those in the art. The polymeric label substrate with
the hydrophilic coating will demonstrate sufficient "wet tack"
during the label application period and the label drying period to
permit containers to be handled and processed. The polymeric film
based facestock will provide a label with printability, chemical
and dimensional stability, resistance to cracking, tearing,
creasing, wrinkling or any other degradation of the sort
experienced by paper labels due to physical or environmental
extremes.
[0026] As used herein, the reference to "a container" includes a
surface of an object made of glass, plastic or metal, such a
dishes, toys, beer bottles, building materials and the like.
[0027] Optionally, if a metalized coating of a thin metal film is
deposited on the polymeric sheets or rolls, premium quality
decorative labels with all of the advantages set forth above will
be provided.
[0028] The hydrophilic component or blends containing the
hydrophilic component will be applied in the present invention to
the selected polymeric sheet in a continuous or patterned layer to
provide the absorptive, wet tack and drying properties that are
necessary to enable polymeric sheets to be successfully used as
label substrates on polymeric or glass containers when applied with
water based wet labeling techniques. The hydrophilic layer which
may be applied by either a coating or an extrusion technique has
the function of absorbing moisture to activate the layer, thus
causing the hydrophilic layer to function as an adhesive without
any additional adhesive or to absorb the moisture from an adhesive
if used and to pass the moisture thru the hydrophilic layer and
micro voided substrate to cause the polymer film to adhere to the
glass, metal or plastic container and to set up rapidly and
positively.
[0029] The choice of polymeric substrate for the label film will
determine the rigidity, deformability or conformability,
regrindability, printability and expansion or contraction
characteristics required for application to the selected container
without the problems associated with paper labels.
[0030] The term "film facestock" or "polymeric label substrate" as
used herein should be taken for purposes of the present invention
to refer to a monolayer, coextruded, coated or laminated material
compatible in terms of rigidity, deformability or conformability,
regrindability if a plastic container and expansion or contraction
characteristics with the plastic, metal or glass container to be
labeled. Similarly, the "hydrophilic layer" previously mentioned
has the properties of wet tack, absorbtivity, drying, sufficient
adhesion to the polymeric label substrate and affinity and adhesion
to the labeling adhesive if used in the wet or dry form.
[0031] It is contemplated that selected hydrophilic layers can be
wet or remoistened without adhesive for use on a glass or plastic
container or a water based adhesive can be used to affix the
polymeric label substrate with the hydrophilic layer to the glass
or polymeric container. For deformable containers, the adhesive if
used, can be selected from those commercially available that are
characterized by the ability to form a bond with the container and
a hydrophilic layer such that when dry, the strength of the
container wall-adhesive interface and the hydrophilic
layer-adhesive interface and the cohesive strength of the adhesive
itself are all greater than the forces required for deformation of
the label.
[0032] As used herein and in the appended claims, the term
"hydrophilic" is used to describe materials or mixtures of
materials which bind, pass or absorb water. The preferred
"hydrophilic" materials are those acrylic polymers which bind or
absorb water. The especially preferred "hydrophilic" material is
DP6-6006, a sodium polyacrylate available from Ciba
Specialties.
[0033] It is also an aspect of the present invention to use
crosslinkable (reactive) components in the hydrophilic layer that
can cure with a catalyst supplied in the hydrophilic layer,
rewetting water or adhesive (if used) that will promote adhesion to
the labeled container along with chemical and moisture resistance.
Examples of cross-linkable materials include carboxylated synthetic
resins. The catalyst can also be added to the adhesive which could
have reactive components which would cure the adhesive and
hydrophilic layer together. Examples of crosslinkable components
include zirconium salts of mineral acids, polyfunctional aziridine,
water soluble polyamide-epichlorohydrin material such as Polycup
172, zinc ammonium carbonate and the like which may be used at a
level of 0.2-8% by weight of the adhesive composition.
[0034] The coated, extruded or coextruded hydrophilic layers
functionality can be defined as a substance capable of combining
two surfaces by the formation of a bond whether it is a moist
hydrophilic layer to glass or polymer or a dry hydrophilic layer to
a wet labeling adhesive which as an intermediate layer that bonds
to both the hydrophilic layer and glass or polymer of the container
when dry.
[0035] The use of the proper hydrophilic layer for a given
polymeric labeling substrate and container to be labeled will have
a direct effect on the speed which the labeling line can be
run.
[0036] When considering the choice of the material which forms the
hydrophilic layer, which may be applied by coating, coextrusion or
extrusion, one must consider the label substrate, container to be
labeled, labeling machinery, water or adhesive application
technique and down stream processing requirements such as filling,
conveying and packing. Generally a thickness of from 0.1 to 8 mils
of the hydrophilic layer, when dried, may be employed on the
polymeric film layer, depending on the particular hydrophilic
material that is selected.
[0037] It is critical to the successful application of a
hydrophilic polymeric film label to control how the water or water
based adhesive is applied to the hydrophilic layer, how deposition
(weight or thickness) is controlled and how the resultant
combination with the container is pressed together. Generally, from
0.25 to 6 mils of water or water based adhesive is applied to the
hydrophilic layer with 100% coverage of the label. If a grid or
other pattern of adhesive is employed, then the overall amount of
adhesive consumed is reduced. If a grid pattern is employed, the
hydrophilic layer may be applied to be substantially in register
with the adhesive layer. It will generally be possible to reduce
the typical amount of adhesive applied to a label when using the
hydrophilic layer of the invention to an amount which 20-80% of the
amount that is typically employed for affixing paper labels to a
surface. The choice of the hydrophilic layer and the type of label
substrate and container to be adhered together, as discussed above,
the plant processing conditions after labeling, storage
requirements and the end use requirements that must be met such as
high temperature resistance or ice proofness and the choice of an
intermediate adhesive layer are important considerations. There are
many more specific variables within these considerations all of
which influence the formulation of the proper hydrophilic layer and
adhesive (if used) for a specific application.
[0038] Mechanical adhesion is defined as the bonding between
surfaces in which the adhesive holds the parts together by
inter-locking action and actual physical penetration. Specific
adhesion is the bonding between surfaces which are held together by
molecular forces wherein the surfaces are non porous and no
penetration is possible.
[0039] These forces are related to the polarity and size of the
molecules and the initial action in obtaining a bond when the
hydrophilic surface is wet and a bond develops through molecular
forces.
[0040] In mechanical as well as specific adhesion, the optional
hydrophilic layer with optional intermediate adhesive layer must
"wet" both surfaces completely or weak bonded areas will develop as
it dries or "sets" resulting in a poor bond. Not only is wetting of
the surfaces critical, penetration is also important. Penetration
is important since most combinations of surfaces to be adhered
together involve at least one porous or absorptive surface which
controls the "setting" characteristics. To facilitate specific
adhesion, wetting of the surface and penetration are critical for
the hydrophilic layer or hydrophilic layer with intermediate
adhesive which must be in a fluid state. For purposes of this
invention, this is accomplished by applying water or water based
adhesive to the selected hydrophilic layer which when applied to
the container to be labeled brings the hydrophilic layer and
container wall into intimate molecular contact. By using a wet
hydrophilic layer or intermediate adhesive which also wets and
penetrates the hydrophilic layer as well as the container surface,
a fluid region is created that flows to cover the surface as
completely as possible. This is critical to the invention where
even an apparently smooth surface in reality is composed of a
random network of hills and valleys. When the hydrophilic layer is
in the wet condition, with or without adhesive, it serves as a
wetting bridge to promote adhesion.
[0041] Various commercially available adhesives can be utilized to
provide good adhesion of polymeric film layers to a plastic, metal
or glass surface. These materials include starch based adhesives or
casein based adhesives now predominantly used for glass
applications since they do not bond well to plastic or metal.
Specific adhesives that may be employed include EVA based materials
which have free carboxyl groups, converted starch solutions, PVA
based adhesives, casein based adhesives, synthetic resin
dispersions for metal or plastic containers or blends of synthetic
and starch based products and the like.
[0042] It is clear that one specific hydrophilic layer may not fit
all applications but hydrophilic layers can be tailored to
particular applications based on the conditions and requirements
for wet PML labeling of polymeric substrates.
[0043] If an adhesion promoting tie layer or primer is employed to
promote hydrophilic layer adhesion or adhesive adhesion, materials
such as maleic anhydride, ethyl acrylic acid, carboxylated
polyurethane resin and the like may be employed at levels of 0.1-3
lb/3,000 sq. ft.
[0044] If a cross-linking catalyst is added to the adhesion
promoting tie layer, the ratio of catalyst to adhesion promoting
tie layer may be an amount that is sufficient to cure the adhesion
promoting tie layer. An excess of the catalyst, i.e. 5-25% in
excess of the amount of the catalyst that is required to cure the
adhesion promoting tie layer may be used to provide a portion of
the catalyst at the interface of the adhesion tie promoter and the
hydrophilic layer to increase the moisture resistance of the
hydrophilic layer without decreasing the moisture absorbtivity of
the hydrophilic layer. Additionally, excess catalyst can also be
available to aid in curing of the adhesive.
[0045] Plasticizers such as n-di-octylphthalate may be employed at
a level of 0.5-3% by weight of the adhesive composition to prevent
the polymeric film label from losing flexibility.
[0046] The slip aids and anti-blocking compounds prevent excessive
friction between the hydrophilic layer and the adhesive layer and
also control the effect of ambient moisture levels which may tend
to interfere with the operation of high speed automated machinery
which is used for apply labels. These materials may be used at a
level of 0.5-3% by weight of the hydrophilic composition or may be
coextruded or coated with the low density film and include
materials such as microcrystalline wax emulsions, erucamide disp,
polytetrafluoroethylene compositions, silicone beads, modified
silicone solutions, parafin wax emulsions, high melting
polypropylene emulsions, carnauba wax emulsions, oxidized
ethylene/EVA compositions, micronized polyethylene wax/PTFE
emulsions, micronized polypropylene, micronized fluorocarbons such
as PTFE (Teflon), micronized polyethylene, silica and talc.
[0047] If an antistatic agent is employed, it may be present at a
level of 0.5-3% by weight of the hydrophilic formulation. These
materials include quaternary ammonium salts such as Ethaquad C12,
sulfonated styrene maleic anhydride, sulfonated polystyrene,
sulfonated vinyl toluene maleic anhydride conductive polymers and
organo modified silicones such as Silwet 77.
[0048] Protective coatings may be used to protect the exposed
polymer film of the label when applied at a level of 0.25-4
lbs/3000 sq. ft. using conventional application techniques. These
materials include styrenated acrylics such as OC1043 from O.C.
Adhesives, Inc., Flexon Release Varnish from Manders-Premier.
[0049] If desired a humectant may be added to the hydrophilic layer
at a level of 0.5-3% to provide curl resistance and to impart
layflat properties to the polymeric film labels. These humectants
include urea, polyethylene glycols (such as PEG400), polyvinyl
alcohol, glycerine and the like.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
EXAMPLE 1
[0050] 2.2 mil white oriented polypropylene (OPP) product code
Opalyte from Mobil Chemical with a nominal density of 0.62 was
coated at 4 lb./3000 sq. ft. dry with a 50% solids water based
solution. The solution consisted of a mixture of 50 parts dry of
Dextrin 2723625 from Findley Adhesives and Dextrin compatible
Polyvinyl Acetate homopolymer emulsion binder resin 25-1072 from
National Starch And Chemical. The coated substrate was printed and
cut into individual patch labels which were applied to high density
polyethylene containers on a high speed water based labeler using
water based resin-starch adhesive OC363-20 from OC Adhesives Corp.
at a deposition of 1.5 dry mils in a corn row pattern. There was
sufficient wet tack to prevent label swimming immediately after
labeling through conveying and bulk packing. The labeled containers
dried sufficiently after 8 hours to ship bulk packed to a filling
plant 20 miles away by truck where they were conveyed through a
filling system and packed in cases. When it was attempted to remove
the labels after 3 days, the bond of the label was stronger than
the cohesive strength of the cavitated layer of film which
fractured and left a thin layer of voided OPP over 55% of the
labeled area of the container. It was noted that the adhesive had
penetrated the cellular structure of the voided OPP because the
tack of the adhesive could be felt on top of the fractured
area.
EXAMPLE 2
[0051] Nominal 3 mil white oriented polypropylene (OPP) product
code IML-333 from Applied Extrusion Technologies, with a density of
0.7 was coated at 2 lb./3000 sq. ft. with a 40% solids water based
solution. The solution consisted of a mixture of ASP400P clay from
Engelhard Industries and DP6-6066 sodium polyacrylate binder
polymer as a hydrophilic layer in the dry ratio of 2:1 clay to
binder. The clay binder mixture was catalyzed with CX-100
polyfunctional aziridine at a level of 0.25% based on the total dry
weight of the hydrophilic layer to promote adhesion of the coating
to the substrate and improve water resistance without eliminating
the hydrophilic nature of the coating. The coated substrate was
printed and coated with a protective over lacquer prior to being
cut into individual patch labels which were applied to coextruded
polyester based containers on a high speed water based labeler
using water based starch-resin adhesive 10-7302 from Henkel
Adhesives at a deposition of 2 dry mils in a corn row pattern.
There was sufficient wet tack to prevent label swimming immediately
after labeling through packing. The labeled containers dried
sufficiently at the edges after 3 days at room temperature to
permit handling and use. When it was attempted to remove the
labels, the bond of the label was stronger than the cohesive
strength of the cavitated layer of film which fractured and left a
thin layer of voided OPP over 70% of the labeled area of the
container.
EXAMPLE 3
[0052] A laminate was made which consisted cavitated polypropylene
of trade name (WTL a 2 mil cavitated oriented polypropylene (OPP)
from Applied Extrusion Technologies with a density of 0.7) was
permanently adhered to the underside of a 0.48 mil metalized
polyethylene terephthalate from Advanced Web Products. The
composite structure was assembled using a urethane-acrylic
laminating adhesive (AS284-16 from Adhesion Systems Inc.) applied
at 1.5 lb./3000 sq. ft. and 2% of CX-100 aziridine cross-linker
from Zeneca resins using conventional laminating techniques.
[0053] The OPP side of the laminate was primed with a reactive
primer consisting of a carboxylated polyurethane resin Sancure 1301
from Sancure Industries that was catalyzed with excess (5% wet on
wet) CX-100 polyfunctional aziridine from Zeneca Resins at a
deposition of 0.1-0.2 lb./3000 sq. ft. A coating at 2 dry lb./3000
sq. ft. was applied over the primed surface from a 40% solids water
based solution. The solution consisted of a mixture of ASP400P clay
from Engelhard Industries and DP6-6066 sodium polyacrylate binder
polymer in the dry ratio of 1.5:1 clay to binder. A portion of the
excess aziridine in the primer is available on the surface of the
cured primer to react with active sites in the DP6-6066/Clay matrix
(hydrophilic layer) to promote adhesion of the coating to the
substrate and improve water resistance without eliminating the
hydrophilic nature of the coating. The coated substrate was printed
and cut into individual patch labels which were applied to glass
containers on a high speed water based labeler using water based
adhesive 10-7026 from Henkel Adhesives at a deposition of 3 dry
mils in a corn row pattern. There was sufficient wet tack to
prevent label swimming immediately after labeling through packing.
The labeled containers dried sufficiently at the edges after 1 day
at room temperature or 3 days in cold storage to permit handling
and use. When it was attempted to remove the labels, the bond of
the label was stronger than the cohesive strength of the cavitated
layer of film which fractured and left a thin layer of voided OPP
over 75% of the labeled area of the container. In areas where the
metalized PET could be separated from the OPP, it was noticed that
the adhesive had penetrated the cellular structure of the voided
OPP. This was noticed because the moist surface and wet tack of the
adhesive drying through the cellular structure could be felt on top
of the OPP fractured area.
EXAMPLE 4
[0054] A cavitated polypropylene film from Applied Extrusion
Technologies, (IML 333) with a density of 0.7 was coated on one
side of the film with clay filled acrylic resin at a ratio of 3
parts clay to 1 part resin (PD959-400 from Process Resources Corp.)
at a coating level 1.5 lb/3,000 sq. ft. using 2% CX-100 aziridine
as a cross-linker. The film is printed with label indicia on the
uncoated side and patch labels were cut and applied to glass
bottles using a water based starch-resin adhesive with zinc
cross-linker (AS692-1 from Adhesion Systems, Inc.). After two
weeks, it was determined that the labels were fully dried and
adherent to the glass bottles.
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